1. Field of the Invention
The present invention relates to a main circuit part of a vacuum circuit breaker, and more particularly, to a terminal structure of a main circuit part of a vacuum circuit breaker.
2. Description of the Conventional Art
In general, a vacuum circuit breaker is a circuit breaker installed in a high voltage electric power system to break a circuit to protect the electric power system in the event of a dangerous situation such as a short circuit or an overcurrent, and it is designed by utilizing excellent insulating performance and arc-extinguishing capability in a vacuum state.
The vacuum circuit breaker is categorized into a drawable type vacuum circuit breaker and a fixed type vacuum circuit breaker. That is, the vacuum circuit breaker is divided into a fixed type circuit breaker which consists only of a main body and is fixed to a switch panel, and a drawable type circuit breaker which is configured to have an outer box called a cradle for facilitating the maintenance and repair of the circuit breaker so that a main body is retracted into or pulled out of the cradle.
FIG. 1 illustrates a main body of a drawable type vacuum circuit breaker according to the conventional art. As shown in FIG. 1, the main body 1 of the vacuum circuit breaker includes a main circuit part 2, a manipulation part 3, and a feeding part 4. Among these parts, the main circuit part 2 is an essential one which is operated to apply or break a current and a voltage in the circuit system, and includes an upper terminal 5 connected to a power supply and a lower terminal 6 connected to a load.
FIG. 2 illustrates a current flow of a conventional vacuum circuit breaker.
Referring to FIG. 2, a current applied from a power supply flows into a load via the upper terminal 5, a vacuum interrupter 7, and the lower terminal 6, sequentially.
In such a conventional vacuum circuit breaker, the upper terminal 5 and the lower terminal 6 of the main circuit part 2 are made of copper. As the current carrying capability of the circuit becomes larger, the cross-sectional area of the upper and lower terminals 5 and 6 becomes larger in proportion thereto. However, as the copper has a relatively high weight due to its high density, the upper and lower terminals 5 and 6 of the large-capacity vacuum circuit breaker are configured as a hollow type so as to have a minimum weight, while maintaining a minimum sectional area for current application. Thus, when the vacuum circuit breaker is operated in an inserted state into a cradle (not shown), closed spaces A and B are formed in the upper and lower terminals 5 and 6, as shown in FIG. 3, resulting in high-temperature air within the closed spaces A and B. This may cause the temperature of the upper and lower terminals 5 and 6 to rise. To overcome such a problem, there has been provided a compulsory device such as a cooling fan (cooler 8) or the size of the terminals 5 and 6 had to be much more increased.
However, there have been some problems in that as the size of the terminals 5 and 6 becomes larger, the material cost becomes high and the installation area also becomes large. Further, in a case where the compulsory cooling device is provided, the internal design of the vacuum circuit breaker becomes complicated, the number of components is increased, and the power consumption is increased.
Meanwhile, Korean Patent No. 10-0950129 (Title: Main Circuit Terminal Assembly of Vacuum Circuit Breaker) may be referred to as a prior art of the present invention.